How does this hidden page (stackexchange.com/topbar/inbox) know which Inbox notifications I have/haven't opened?
Both the drop-down
inbox and the API (ie, api.stackexchange.com/docs/me-inbox) seem to mark all my messages as read as soon as I read one.
I'd like to retrieve that data as well (for more than the 25 listed on that page).
Also just to confirm, there's no way to Mark as Unread, correct?

inbox/unreadroute? ... Also, you can get all of your inbox items at stackexchange.com/users/current?tab=inbox.